In general, the rotating machine with brush is configured to hold the brush in the brush holder and press the brush from the back surface with the spring so that the brush is brought into contact with the slipring or the commutator (hereinafter referred to as “metal rotating body”) under the predetermined force. A predetermined current is passed through the brush for the purpose of outputting the generated power to the outside with holding the contact state or supplying power to the rotor for rotation. The brush is designed to maintain good sliding relationship between the brush and the metal rotating body to prevent burnout and abnormal wear caused by the contact failure. In the case where the spring pressure to the brush is strong, the brush is strongly pressed against the metal rotating body. Therefore, the electrical loss is lessened, but the mechanical loss is increased. In the case where the spring pressure to the brush is weak, the brush is not sufficiently pressed against the metal rotating body, which may cause increased electrical loss and vibration of the brush. Therefore, it is necessary to consider various factors, such as the amount of applied current, the rotating speed and the like, for selecting the brush pressing.
JP 2010-124528, for example, discloses a structure which allows the constant pressure to be applied by attaching the elastic material or the adjustment material to the pressure part and allows the pressure to be adjusted depending on the presence or absence of the current flow for the purpose of bringing the brush into stable contact with the metal rotating body.
The rotating machine with the brush and metal rotating mechanism will reduce the replacement cycle of the brush owing to abnormal wear and burnout accident of the brush caused by the contact failure between the brush and the metal rotating body. Accordingly, the contact state between the brush and the metal rotating body is required to be maintained in good condition.
The structure disclosed in JP 2010-124528 is configured to have the adjustment material at the pressure part to vary the pressure for each operating condition. However, good contact state between the brush and the metal rotating body cannot be achieved in the case where the load of the rotating machine is increasing when used and where the contact state is deteriorated between the brush and the metal rotating body.
The present invention provides a rotating machine which can maintain good contact state between the brush and the metal rotating body.